Fibre channel is the name of an integrated set of standards being developed by the American National Standards Institute (ANSI). Fibre channel is a hybrid channel and networking data transport medium.
Fibre channel topology can be selected depending on system performance requirements or packaging options. On fibre channel topologies commonly used in storage area networks is an arbitrated loop. In an arbitrated loop fibre channel topologies, storage devices, such as hard disk storage devices and tape devices, can be used to store data that can be retrieved by a software application. In order to save or retrieve data from any particular storage device, the storage device must first be located.
One method for discovering the location of storage devices on fibre channel storage network is to make an address resolution protocol (ARP) or a fibre channel address resolution protocol (FARP) inquiry. However, many of the storage devices currently in use are legacy SCSI devices that do not support ARP or FARP. Whether the SCSI storage devices are locally attached to the storage router through a SCSI bus, or are contained in an arbitrated loop attached to the storage router through an FCP interface, conventional fibre channel methods of using ARP or FARP inquiries to discover the location of compatible storage devices will not be successful because a SCSI legacy device that does not support ARP or FARP cannot respond to this discovery inquiry.
Without some mechanism to discover these legacy SCSI devices in a storage area network, FARP inquiries from a host computer will be ignored by these SCSI storage devices, the host will not get a reply and will respond as if the storage device does not exist on the storage area network.